Adjustable speaker unit



Jan. 13, 1931. BQXLEY 1,789,270

ADJUSTABLE SPEAKER UNIT Filed Feb. 16, 1927 2 Sheets-Sheet 1 A TTORNEYS.

Jan. 13, 1931. F. BOXLEY 3,789,279 1 ADJUSTABLE SPEAKER UNIT Filed Feb.16, 1927 2 Sheets-Sheet -2 IN V EN TOR.

A TTORN E YS.

Patented Jan. 13, 1931 UNITED STATES FREDERICK BOXLEY, F OAKLAND,CALIFORNIA ADJUSTABLE SPEAKER UNIT 'Application filed February 16, 1927.Serial No. 168,815.

This invention relates to sound reproducers such as employed inconjunction with radio receiving sets or phonographs which reproduce andamplify sound through vacuum tubes and the like, and especially to anadjustable attachment which will afford a considerable rangeofmodulation in quality, volume, intensity, flexibility, etc., of thesound or tones reproduced.

Those who have studied the physics of sound even superficially will knowthat every body has a sound frequency period of its own. For instance, atuning fork may have a period vibration of exactly 256. This isdetermined not only by the physical dimensions of the fork but also byits shape. A wooden box, a metal bar, a plate; all such things havetheir own frequency periods and the speaker diaphragm is no exception.Every diaphragm used in. a telephone or loud speaker has its own specialsound period which will depend upon (1st) the thickness of thediaphragm, (2nd) the diameter of the diaphragm, (3rd) the shape thereofand 1th) the particular material from which it is constructed.

There is always one particular frequency which will find the diaphragm'most sympathetic and which will represent its highest point ofefiiciency. This statement should not be construed to mean that adiaphragm cannot be made to vibrate to sounds having a frequency aboveor below this natural period but it should be construed to mean that itis physically impossible for the diaphragm to reproduce otherfrequencieswith the same degree of faithfulness that it is able to reproduce afrequency at or near that of its own period. With conditions existing asabove stated, one cannot expect a loud speaker to respond perfectly tothe Woodwinds, bass viols. kettle drums and brasses of a symphonicorchestra, nor can one expect such ,a diaphragm to respond with equalefficiency to the voices of baritones, tenors, contraltos,

- Sopranos, etc.

The sound reproducing qualities of a diaphragm is also affected by otherfactors which tend to render the tones hard, harsh,

m shrill and penetrating, or conversely, low, in-

distinct, muflled and jumbled; These factors may be caused byoverloading of the magnets by which the diaphragm is actuated,

by improper adjustment of the reed or armature with relation to themagnets and dia- 65 phragm, by lost motion between the connected parts,by improper leverage connections and by variation in impedance betweenthe last vacuum tube of a receiving set and the impedance of the coil ofthe speaker unit, etc. The sound reproducing qualities of a diaphragm isalso affected by variation in the modulated current flowing through thecoils whereby the armature is aflected, i. e., if a, receiving set islocated within a few blocks of a broadcasting station, the modulatedcurrent flow through the coils may be so strong as to cause the armatureto vibrate excessively thus producing a blasting or vibrating sound.Again it is possible that a broadcasting station may be at such adistant point that the modulated current flowing through the coils is soWeak that the armature will not be affected and no sound will bereproduced or at least will be so faint as to be of no practical value.

The object of the present invention is to generally improve and simplifythe construction and operation of sound reproducers of the characterdescribed, to provide an adjustable attachment whereby the diaphragm ofa, sound reproducer will be caused to vibrate at highest efliciency, toprovide an adjustable attachment whereby the tone quality of the soundreproduced may be modulated to produce clear tones, to increase volume,etc. And further to provide an adjust-able attachment whereby aresistance may be imposed upon the armature and the diaphragm when themodulated current flow is excessive and whereby the resistance may bematerially decreased when the modulated current flow is Weak as whenreceiving from distant broadcasting stations. The invention is shown byWay of illustration in the accompanying drawings in which Fig. 1 is afront view of a loud speaker unit showing the application of theinvention,

D which is Fig. 2 is a central vertical section taken on. line IIII,Fig. 1,

Fig. 3 is a perspective view of the adjustable mechanism whereby thereed arm is supported,

Fig. 4 is a perspective view of yoke,

Fig. 5 is a perspective view of the reed arm and the connecting rodsattached thereto,

Fig. 6 is a perspective view of the bearing block,

Fig. 7 is a perspective view of the slidable support,

Fig. 8 is a perspective view of the tension sprmg,

Fig. 9 is a perspective view of the main supporting plate,

Fig. 10 is a side elevation of a reed type of speaker unit,

Fig. 11 is a side elevation of a modified form of a reed type of speakerunit.

Referring to the drawings in detail and articularly Figs. 1 and 2, Aindicates a liase plate on which is supported a permanent'magnet B, areed arm C, an armature ositioned betweenthe poles of the magnet andcoil windings E through which the modulated current from the tubes orreceiving set is directed. I

A standard balanced or pivoted armature type of speaker unit isillustrated in Figs. 1 and 2, the armature D is shown as being centrallypivoted as at F. It will be noted that the armature D is connectedthrough rod 2 with the reed arm C and that this is in turn connectedwith the diaphragm G through means of the rod 3. The armature iscentrally suspended on delicate bearings between the poles of thepowerful permanent magnet and since the pulling force of each pole ofthe magnet is equal and in op-,

- posite directions, no strain is placed on the diaphragm when thespeaker is not in use. The armature is also disposed between the coils Eand the modulated current impulses from the radio set are permitted toflow through these coils. This modulated or fluctuating current causesthe armature to vibrate in the permanent magnetic field and thesevibrations are transferred through the rod '2 to the reed arm C and fromthe reed arm through the rod 3 to the diaphragm, and the diaphragm isthus made to keep in step with the armature.

The majority of loud speakers placed on the market have a fixed orpermanent connection between the armature D and the diaphragm G andwhile a particular type of speaker may operate to fair satisfaction witha certain type of receiving set, it may be entirely unsuited to anothertype of set due to the variation of impedanceand other factors. In thepresent instance the vibratory movement of the armature is firsttransmitted to a reed arm and then to the diaphragm of the speaker. Areed arm of considerable length is employed and means are provided forincreasing or decreasing the point of bearing of the reed arm, the meansemployed being best illustrated in Figs.. 2 and 3' and being generallyindicated by the reference character H. The mechanism H is an adjustablebearing which is adapted to engage and support the reed arm C at anypoint intermediate the rod 3 and the bearing block 4. This bearing isconstructed as follows:

.Formed in the base plate A is an elongated receive a. clamping nut 8.Interposed between the T-shaped block and the base plate A- is anelongated tension spring 9 which is provided with a central rectangularshaped opening 6?) to permit the extension 6a of the block to passtherethrough. Straddling the upper end of the T-shaped block is abearing block 10. This block is provided with bevelled ends 10a and withtwo interspaced foot extensions 106 which are adapted to engage theupper surface of the tension spring 9 on opposite sides of the T-shapedblock, these foot extensions being padded as indicated at 100. The reedarm C is disposed in parallelism with the base plate A in alignment withthe elongated slot 5 formed therein. It passes over the bearing block 10and is supported thereby and it is adapted to be clamped to the bearingblock and the base plate by means of a yoke-shaped member 11 whichstraddles it and which is secured to the T-shaped block by means ofscrews 11a. When the several parts of the adjustable bearing H areassembled as shown in Figs. 2 and 3, and if it is desired to adjust thepoint of support, it is merely necessary to loosen the clamping screw 8and then to slide the adjustable bearing one way or another in thelongitudinal slot 5. If it is desired to decrease the lever action ofthe reed arm C with relation to the armature and the diaphragm G, theadjustable bearing is moved inwardly in the slot 5 in the direction ofarrow a (see Fig. 2), if it is desired to increase the length or leveraction of the reed arm with relation to the armature and the theadjustable hearing as a whole at the point.

of adjustment and it will at the same time form a support for the reedarm. The adjustable connection between the armature and the diaphragmhas been found to be of great importance as the tone quality of thesound reproducer may be considerably improved or the sound reproduced asa whole may be rendered more sensitive to reception from broadcastingstations located at a great distance, etc. For instance, if the tonesseem to be low or muflied, a slight tightening action on the screw 8 maybe all that will be required to clear the tones. Conversely, if thetones are shrill or sharp, it may be remedied by a slight slackening ofthe screw, etc. That is, the adjustable bearing does not only serve thefunction of increasing or decreasing the lever arm action of the reedarm C and the ratio of movement between the armature and the diaphragm,but it also serves the function of adjusting the armature D withrelation to the pole pieces. For instance, by tightening the screw 8 andcompressing the tension spring 9, a downward pull may be exerted on therod 2 which is suflicient to tilt the armature about its central pivot,thus bringing the pivot ends ,of the armature into closer proximity tothe pole pieces or vice versa.

If a receiving set employing a loud speaker is positioned fairly closeto a broadcasting station, it is possible that the modulated currentflowing from the tubes through the coils of the speaker is so strongthat the tones reproduced tend to vibrate and blast. In such an instancethe tone quality may be materially improved by moving the adjustablebearing longitudinally of the reed arm in the direction of arrow (1.This decreases the ratio movement between the armature and the diaphragmand it will at the same time impose a resistance which will tend tofurther decrease the movement of the armature and diaphragm. 011 theother hand, if theperson is listening in to a broadcasting stationlocated several hundred, one thousand, or more miles away, it ispossible that the modulated current flowing from the tubes to the coilsof the speaker are so weak that the armature is not sufiicientlyaffected to operate the diaphragm. In that instance the adj ustablebearing 10 is moved outwardlv on the reed arm in the direction ofarrow7). action is thus increased, the resistance is materially reduced andthe armature will thus be more sensitive and easily afit'ectedbytheweaker currents. In other words, with an adj ustment of this characterit is possible to listen in to different stations which-otherwise wouldnot be heard. It might be stated that the adjustments provided servethree main functions 1st, that of increasing or decreasing the lever armaction between the armature and the diaphragm, 2nd, that of increasingor decreasing resistance imposed upon the armahe lever arm ture anddiaphragm, and 3rd, that of adjusting the armature with-relation to itspole pieces. This is also of considerable importance, particularly whenlistening to a distant station as the modulated currents passing throughthe coils of the speaker are in some instances so weak that the polepieces are not materially affected, and in that instance, it isnecessary to adjust the armature so as to assume a position in as closeproximity to the pole pieces as possible. Suffice. it to say that theadjustments provided permit a wide range of tone modulation. It

also permits a speaker or sound reproducer to be adjusted to be moreresistant or vice versa or more sensitive as conditions may require. Italso permits adjustments which will render diaphragms of varyingdiameters, thicknesses, shapes. etc, more efficient withrelation to theoutput of the radio set or amplifying instrumentthan would otherwise bethe case. Referring to Figures 2 and 5, it will be noted that the reedarm increases in thickness from end to end, it being thinnest orlightest at the end adjacent the armature and proportionately heavierat'the opposite end. This is important as the resistance imposed uponthe armatureand diaphragm may accordingly be varied to a considerabledegree when the bearing H is adjusted longitudinally of the reed arm. Itshould also be noted that a pad A1 is interposed between the shown asattached to a balanced or pivoted armature type of speaker. 11 theadjustable bearing is shown as at tached to reed types of speaker units.For instance, in Fig. 10 areed 15 is shown as rigidly secured andsupported on a bearing post 16. This reed extends between the poles ofthe magnet and also serves the function of an armature, the free end ofthe reed is in this instance connected with the main reed arm C-by meansof a rod 2a and the main reed arm is in turn connected with diaphragmnot here shown by a rod 3a. The adjustable bearing H is identical inconstruction to that shown in connection'with Figs. 1 and 2 and isadjustable and operable in the same manner, the only difference beingthat two tension springs are employed as indicated at 9 1 and 9a. Thespring 9a on the rear side of the base plate may or may not be. employedas desired, the same bein true of the other units disclosed. In theF1g.' 11, the main reed arm is again indicated at C while the arma- InFigs. 10 and.

ture reed 2b is shown as directly connected or attached to the free endof the reed arm C without any intermediate connection as illustrated inFigs. 2 and 19. The adjustable bearing H is also employed in thisinstance and the lever arm action may accordingly be increased or,decreased as conditions may demand.

While certain features ofthe present invention are more or lessspecifically described and indicated, I wish it understood that variouschanges may be resorted to within the scope of the appended claims;similarly, that the materials and finish of the several parts employedmay be such as the manufacturer may dictate or varying conditions oruses may demand:

said reed arm having a lever. arm action between the armature and thediaphragm and means for increasing or decreasing the length of lever armaction between the armature and the diaphragm.

2. The combination with the vibrating armature and the diaphragm of asound reproducer of a reed arm connected with the armature at one end, abearing member sup-. porting the opposite end of the reed arm, said reedarm functioning as a lever arm between the armature and the diaphragmand means for adjusting the bearing longitudinally of the reed toincrease or decrease the length of the lever arm. a

3. The combinatibn with the vibrating armature and the diaphragm of asound reproducer of a reed arm connected with the armature at one end, abearing member supporting the opposite end of the reed arm, said reedarm functioning as a lever arm between the armature and the diaphragmand an adjustable bearing movable longitudinally of the reed arm toincrease or decrease the length of the lever arm action.

4. In a sound reproducer, a balanced armature, pole members cooperatingwith the armature, a diaphragm connected with the armature, and a meansfor varying the ratio of movement of the diaphragm with relation to thebalanced armature.

5, In a sound reproducer, a balanced type of armature, pole memberscooperating therewith, a diaphragm, a reed arm connected at one end withthe bearing armature, a fixed bearing member supporting the opposite endof the reed arm, a connection between the reed arm and the diaphragm andan auxiliary bearing member adjustable longitudiarmature at one end, asupport for the opposite end of the reed arm, a connection between thereed arm and the diaphra 111, said reed arm having a lever arm actionetween the armature and the diaphragm, means for increasing ordecreasing the length of lever arm action between. the armature and thediaphragm, and means whereby the movement of the armature and thediaphragm may be variably resisted.

7. The combination with the vibrating armature and the diaphragm of asound reproducer of a reed arm connected with the armature at one end, asupport for the op posite end of the reed arm, a connection between thereed arm and the diaphragm, said reed arm having a lever arm actionbetween the armatureand the diaphragm, means for increasing ordecreasing the length of lever arm action bet-ween the armature and thediaphragm, means whereby the movement ofthe armature and diaphragm maybe variably resisted, and means whereby the position of the armature maybe ad usted with relation to pole pieces cooperating therewith. r

8. The combination with the vibrating armature and the diaphragm of asound reproducer of a reed arm connected with the armature at one end, asupport for the reed arm and adjustable longitudinally of the reed arm,and a connection between the diaphragm and the reed arm at a pointintermediate the armature and the adjustable support.

9. The combination with the vibrating armature and the diaphragm of asound reproducer of a reed arm connected with the armature at one end, asupport for the reed arm and adjustable longitudinally of the reed arm,a connection between the diaphragm and the reed arm at a pointintermediate the armature' and the adjustable support, and meanspermitting'vertical adjustment of the longitudinal adjustable support.

FREDERICK BOXLEY.

